The differentiation of pulpal cells into odontoblasts during pulpal healing will be studied in two model systems with a view to developing a biological method of pulp capping. 1. An in vitro model using enzymatically separated bovine pulp cells grown in monolayer initially and subsequently in a three dimensional cell plug system. Cells from various concentric regions of the bovine pulp will be stimulated to differentiate into preodontoblasts or odontoblasts and possibly form predentine and dentine, by biological 'materials' such as dentine, predentine, enamel, reduced enamel epithelium, and root sheath. Cells will be cultured against several inert surface variables: Millipore filter (0.45 um and 0.1 um, both sides of the filter), cellophane, Teflon, isobutyl cyanoacrylate, and paper. The surfaces will be modified as appropriate. The commonly used endodontic materials, suitably modified for in vitro experiments will also be investigated. Enzyme histochemical methods will be used to follow the differentiation of the cells involved. 2. An in vivo model system using young dogs. Pulps of dog incisor and cheek teeth will be surgically exposed and treated with the more successful materials and surface modifications from the first model system. Fundamental information of the cell biology of odontoblast differentiation will be obtained.